According to [1]}, the objective function of the problem must be
convex with respect to the coupling variables, which are the power exchange
variables. However, (REF ) is not convex with
respect to the \(P^{e}\)  variables, causing convergence issues when solving the
dual problem with the iterative procedure described in Section II.
Therefore, a power transfer cost function is added in the objective function to
resolve this issue. This new term, which is assumed quadratic to convexify it,
represents the cost of power transfer for the use of the distribution network,
which should be paid to the distribution network operator, and is defined
as follows:
\(\gamma (P_{n,m}^{e}) = \beta (P_{n,m}^{e})^{2}\) 
